with my A12 28mm and 50mm Modules the DNGs taken with an ISO Speed of 100 aka low Iso are 1 Stop brighter than the ones taken at the original ISO speeds of the GXR. The sensor base speed seems to be ISO 200 and ISO 100 was intro ducted later via firmware update i think.

Anyway using Apple Aperture, the ISO100 DNGs are all 1 stop brighter than the JPGs and all other DNGs taken at other ISO speeds.